As a next-generation semiconductor device material, SiC (silicon carbide) is expected. SiC has excellent physical properties, compared with Si (silicon), including the band gap being three times, the breakdown field strength being about 10 times, and the thermal conductivity being about three times, as large as those of Si. If these properties are used, a semiconductor device operable at a high temperature with a low loss can be realized.
In transistors using SiC, it is desired to a decrease on-resistance to realize large on-current. As a structure that decreases the on-resistance, there is a vertical transistor having a trench gate structure in which a gate insulating film and a gate electrode are provided in a trench.